Algorithm Research Of Synchronization System In GB Digital Television Receiver

In recent years,the digital television with its advantages of high-definition screen, high spectrum utilization efficiency,flexible transmission and many interactive business operations,has been widely concerned.The chinese digital terrestrial television broadcasting standard with independent intellectual property,named "Frame structure,channel coding and modulation for digital television terrestrial broadcasting system" has been published,which stands for DTMB in english. Therefore,research on terrestrial transmission technique according to digital television standard of our country has far-reaching meaning.Synchronization of digital TV technology in the communication system occupies a very important position.Especially,the multi-carrier system with OFDM (Orthogonal Frequency Division Multiplexing) technology,needs more stringent synchronization requirements.Synchronization error will not only cause inter-symbol interference,but also cause inter-channel interference,and adversely affect the receiver's performance.This article based on the current development of digital television,has deeply analyzed and researched the synchronous problems and some typical time-frequency synchronization algorithms in the OFDM system,and brings forward a frame and carrier synchronization algorithm design based on the PN(Pseudo-random Noise sequence) correlation for the multi-carrier mode in DTMB system,which has advantages of low implementation complexity,good synchronization performance, and wide range and high precision of carrier frequency offset estimation.In the frame synchronization,the sub-parallel matching non-coherent de-spread technology is used to capture PN sequence more quickly,and in the carrier synchronization,the block average and the non-block average frequency offset estimation algorithm performance are compared,and according to both their own characteristics,we can use the block average algorithm by its wide range estimation characteristic to proceed coarse frequency offset estimation and then use the non-block average algorithm by its high precision estimation characteristic to proceed fine frequency offset estimation,can achieve a very good estimation performance. The simulation results show that:the frame synchronization algorithm obtains good performance in AWGN channel,static multi-path channel(Brazil D) and dynamic multi-path channel(ATTC3).The estimation precision of non-block average algorithm is better than the other both in AWGN channel and ATTC3 channel,but much smaller estimated range.Using the combined method(block average algorithm to proceed coarse frequency offset estimation and then non-block average algorithm to proceed fine frequency offset estimation) can well estimate within 150kHz frequency offset both in AWGN and ATTC3 channel and the estimation error is less than 0.2Hz in AWGN channel and not more than 27.5Hz in ATTC3 channel,greatly meeting the requirement that when there is at dozens of sub-carrier frequency offset in the system,the corrected frequency offset doesn't exceed 40Hz.Therefore,a very good performance can be achieved by using PN as frame header in DTMB system.